Figure 2

Distribution patterns of SRLKs and SRLCKs and classification of SRLKs. The ML phylogenetic tree (Additional file 1: Figure S1) was displayed in circular form to show the classification of SRLKs (subgroups 1a-1f and 2a-2g are evident in each of the SD-1 and SD-2 groups) and the distribution patterns of SRLKs and SRLCKs from five land plants (electric blue for moss; bright green for spikemoss; deep pink for rice, orange for poplar, and blue for Arabidopsis). The roots are shown by branches in filled black lines and the aLRT bootstrap values of the major internal nodes are indicated by numbers. Predicted two gene fusion events are labeled by branches in black, the minor fusion event is indicated by black arrow.